1. Field
This disclosure relates generally to communication systems and equipment, and more specifically to techniques and apparatus for allocating communication system resources to mobile devices in the communication system.
2. Related Art
Many wireless communication systems use base stations to communicate with one or more mobile devices (i.e., user equipment or “UE”) within a cell served by the base station. Data sent from the base station to the user equipment is transmitted through a wireless channel referred to as a downlink channel, and data transmitted from the user equipment to the base station is transmitted through a wireless channel referred to as an uplink channel.
The wireless communication system has limited resources that can be allocated to the mobile devices and normally attempts to do the allocation in order to maximize the use of the bandwidth available in the uplink and downlink channels. For example, a frequency, or set of frequencies, is a resource that can be allocated to the mobile device to use for wireless transmission or reception. A time for transmission, or a transmission “time slot,” is also a resource that can be allocated to the mobile device to use for wireless transmission or reception.
With regard to transmitting on the uplink channel, transmit power is a resource that can be allocated to the mobile device to use for wireless transmission. The proper allocation of transmit power is needed so that the base station receives relatively even power levels across the spectrum used by the mobile devices. Proper transmit power allocation also helps to avoid interference with transmissions from other mobile devices, whether those other mobile devices are in the same cell or an adjacent cell.
Power received at the base station can be affected by the distance between the mobile device and the base station, and other types of pathloss between the mobile and base. Distance-dependent path loss reduces the power of the receive signal because of the distance the signal travels. In addition, power can be reduced through shadowing, which occurs when an object comes between the mobile device and base station. For example, if a person with a mobile device walks down a street and a building comes between the mobile device and that base station, pathloss increases due to shadowing.